17 



Drummond, in bis striking and well-known book, " The Natural 

 Law in the Sp ritual World, " might have given us a chapter on 

 parasitism in its relations to the interesting subject now before us. 



Examine a lichen— a fertile one — and you will see some little 

 plate-like bodies, sometimes with a thickish margin and sometimea 

 without, sometimes of the same colour as the thallus and some- 

 times of a different one. These are the apothecia — the so-called 

 fructification — which contain the asci, along with certain threads 

 called paraphyses. The asci may be likened to a row of tiny soda- 

 water bottles turned upside down, and containing spores. These 

 latter are splendid microscopic objects. Their number is constant 

 in the same species, and is usually four or a multiple of four — very 

 often eight. There may, however, be only one, and there may be 

 over a hundred. In their form there is the greatest variety. They 

 are not commonly 07ie-celled, as they are very apt to double their 

 number by each one dividing into two, and, as the case may be, 

 they are said to be 2,-4,- 6,-8, or multi-septate. They require 

 rather a high power — say 400 diameters — with yom- microscope, 

 but they are amongst the most interesting of objects, and wonder- 

 ful enough to be warmly commended to the notice of any Micros- 

 copical Society. The idea that a spore is always a tiny round simple 

 cell is quite a mistaken one, for, in its numerous forms and variety 

 of colours, it delights the student. On the surface of the lichen- 

 thallus, generally at or near the margin, are little blackish spots 

 called spennagones which contain spermatia, and are supposed to 

 fertilize the spores of the apothecia. The Spermatia are exceedingly 

 small, and not provided with any cilia, so that they do not resemble 

 zoospores, which can, for a time, move about freely. Dr. M. C. 

 Cooke, in his " Introduction to the Study of Microscopic Fungi," 

 has a very good ch^ipter on spermagones. Speaking of the dis- 

 charge of the spermatia from the spermagone he says — " to com- 

 pare minute things with gigantic, as a recent author has observed, 

 it resembles the lava issuing from the crater of a volcano." Bear 

 in mind that spermagones are not peculiar to lichens and that they 

 are commonly but not always found on the same thallus as the 

 apothecia. Some lichens have neither apothecia nor spermagones, 

 but are more or less covered with soredia — powdery heaps of 

 gonidia they are — and by means of them the species are repro- 

 duced. This is a genuine illustration of vegetative reproduction, for 

 the old plant throws off part of itself to form its like as many 

 plants, for instance one of the Garlics common on our cliff, throw 

 off bulbils to continue their species. 



Any lengthy remarks on the classification of lichens would be 

 out of place this evening. Nylander, De Bary, Tulasne, Aoharius, 

 Leighton, Orombie, Fries, (and others), have performed the difficult 



